1. Field of the Invention
This invention relates to a package device and a method for making the same, more particularly to a packaging substrate device, which has relatively high heat dissipation efficiency and is suitable for a chip on board (COB) packaging process, a method for making the packaging substrate device, and a packaged light emitting device.
2. Description of the Related Art
During emission of light, light emitting diodes (LEDs) can generate considerable heat that affects adversely the lifetime and power efficiency of the LEDs. When the temperature of the LEDs is increased to above 100° C., the lifetime and power efficiency of the LEDs will be reduced rapidly. Thus, it is necessary to package the LEDs by using package devices with better heat dissipation efficiency to prolong the LEDs' lifetime and to maintain high power efficiency of the LEDs.
In order to increase the heat dissipation efficiency, packaging substrate devices are commonly used nowadays. In a process for packaging a high-power LED using a packaging substrate device, a LED die is first mounted on a heat dissipation sheet using solder paste or heat dissipation paste to reduce a thermal resistance of the packaging substrate device. Then, the heat dissipation sheet is mounted onto a heat dissipation substrate using solder paste or heat dissipation paste such that the heat of the heat dissipation sheet can be transferred to the heat dissipation substrate. Generally, a heat dissipation sheet with large thickness has an efficient heat dissipation efficiency. A heat dissipation substrate associated with such a heat dissipation sheet must be able to dissipate heat rapidly and must possess sufficient structural strength in order to efficiently dissipate heat to the outside. Commonly used heat dissipation substrates include metal core printed circuit boards (MCPCB) and ceramic substrates.
With increasing development of LED technologies, the power efficiency of the LEDs is getting higher and higher. Thus, there is a need to develop a packaging substrate device with a reduced thermal resistance between the LED die and the substrate.